Fine brush pixelation problems

[MrSnotblock]

Hello,
I am a newbie to this forum even though I have used GIMP for a few years, but only on a PC running Ubuntu Linux. I had no problems till I changed to a Mac and now I cannot get a fine line without a lot of coarse pixelation/spatter on the 1 - 5 pixel wide round and fuzzy brushes. This is a problem as I use GIMP for illustration, mostly fine pencil and watercolour effects.
I recently upgraded from an old MacBook to a Mac mini running Lion, but the problem is still there.
Does anybody have any suggestions?
Many thanks

[Rod]

Did you check to make sure Jitter wasn't enabled?(brush tool options dialog)

[MrSnotblock]

No it's not enabled.

Thanks for your reply Rod

[Arzoroc]

Hm .. I cannot really follow your description, can you add a screenshot of your problem? This makes things easier for us I guess.

[MrSnotblock]

Hm .. I cannot really follow your description, can you add a screenshot of your problem? This makes things easier for us I guess.

Thanks Arzorock and Rod. I believe I have solved the problem and the answer is embarrassingly obvious if I had thought harder about it in the first place. I used to work with huge picture sizes and move things around, usually I couldn't see a lot of what I had drawn. Of course, when you zoom in on any area of such a canvas at 200% or even 400% you still have a lot of pixels to play with.

I just remembered this, as I have been working with smaller pictures, rarely larger than 1000 x 700.

I worked it out with a downloaded painting by Tissot "On the Thames", that is only about 700 x 1000 in size. When you zoom in the dreaded pixellation is there too. I've tried to upload part of the painting that I "vandalised" along with this post.

D'Oh!!! I should have seen this. Sorry to waste your time.